1. Field of the Invention
The present invention relates to a date-and-time management device for managing date-and-time effective in a company or officially, and a signature generation apparatus for realizing a signature-with-time-stamp using the managed time.
2. Description of the Related Art
The date-and-time management device is required to manage the time of manufacture of products, for example, in a manufacturing industry, and is also required to realize a signature-with-time-stamp using the managed time. For example, the amount written on an electronic receipt can be prevented from being falsified by entering an officially authorized date-and-time.
In the date-and-time setting system for the date-and-time management device, there are some features as follows. First, only a specified date-and-time manager is allowed to set a date-and-time. Second, any unspecified date-and-time manager can also be allowed to set a date-and-time. Third, a user can specify a date-and-time manager. Fourth, the date-and-time set when a date-and-time management device is delivered cannot be amended.
For example, in the case of a signature-with-time-stamp device, there arises the problem with the effectiveness of the signed date-and-time if a unspecified date-and-time manager can be allowed to set a date-and-time, or if a user can freely specify a date-and-time manager. Therefore, it is normally designed to allow only a specified date-and-time manager to set a date-and-time.
However, considering an actual operation, an officially valid signature-with-time-stamp can be requested, or a signature-with-time-stamp effective only in a specified organization such as a company, etc. can be requested. Therefore, it is desired that the valid range of a signature can be almost freely set on an operation side. However, it has not been possible for conventional date-and-time management devices or signature-with-time-stamp devices to flexibly manage the valid range of a date-and-time to be managed.